Powder and Tongue River Basins (6)
June 1999

Snow
Cool weather has slowed the normal melting of snow -- consequently the comparison to average is exaggerated. The Upper Tongue River drainage is 142 percent of normal (855 percent of last year). Goose Creek drainage is 93 percent of average (Last year Goose Creek was melted out by this time of the year). Clear Creek drainage is 167 percent of normal (last year Clear Creek had melted out by this time.). Crazy Woman Drainage is 269 percent of normal (last year Crazy Woman Creek had melted out by this time). The Upper Powder River is 192 percent of normal (last year the drainage was nearly melted out by now). The Powder River basin snow water equivalent (SWE), in Wyoming, is about 174 percent of average (nearly melted out by this time last year). For more information see Basin Summary of Snow Courses at beginning of report.

Precipitation
May precipitation was 105 percent of average for the 11 reporting stations (315 percent of last year). Monthly percentages range from 53 to 135 percent of average. Precipitation for the year ranges from 108 to 145 percent of average. Year-to-date precipitation is about 122 percent of average in the basin; this is 131 percent of last year at this time.

Reservoir
Tongue River Reservoir storage is currently about 135 percent of average (243 percent of last year). About 65,000 acre feet (96 percent of the total capacity) are presently being stored, compared to 26,800 acre feet last year. The total reservoir capacity is about 68,000 acre feet. Detailed reservoir data is shown on the following page and on the reservoir storage summary at the beginning of this report.

Streamflow
The following runoff values are for the 50 percent probability during the June through September forecast period. The estimated yield for Tongue River near Dayton is 70,000 acre-feet (91 percent of normal). Water users on the Middle Fork near Barnum should have a yield near 8,250 acre-feet (104 percent of normal). The North Fork of the Powder near Hazelton should yield about 7,300 acre-feet (122 percent of normal). The estimated yield for Clear Creek near Buffalo is 32,000 acre-feet (114 percent of average). Rock Creek near Buffalo will yield about 19,300 acre-feet (115 percent of normal), and Piney Creek at Kearny should yield about 36,700 acre-feet (115 percent of average). 

==================================================================================================================================
                                                   POWDER & TONGUE RIVER BASINS
                                               Streamflow Forecasts - June 1, 1999
==================================================================================================================================
                                              |  <<====== Drier ======  Future Conditions  =======  Wetter =====>>  |             
                                              |                                                                     |
  Forecast Point                     Forecast |  ==================== Chance Of Exceeding * ======================  |
                                      Period  |    90%       70%    |  50% (Most Probable)  |      30%       10%    |  30-Yr Avg.
                                              | (1000AF)  (1000AF)  |   (1000AF)  (% AVG.)  |    (1000AF)  (1000AF) |    (1000AF)
====================================================================|=======================|=====================================
TONGUE RIVER nr Dayton (2)           JUN-SEP        54        64    |       70        91    |        76        86             77
                                                                    |                       |
MIDDLE FORK POWDER nr Barnum         JUN-SEP      4.99      6.93    |     8.25       104    |      9.57     11.51           7.90
                                                                    |                       |
NORTH FORK POWDER nr Hazelton        JUN-SEP      5.81      6.70    |     7.30       122    |      7.90      8.79           6.00
                                                                    |                       |
CLEAR CREEK nr Buffalo               JUN-SEP        21        28    |       32       114    |        36        43             28
                                                                    |                       |
ROCK CREEK nr Buffalo                JUN-SEP      15.4      17.7    |     19.3       115    |        21        23           16.8
                                                                    |                       |
PINEY CREEK at Kearny                JUN-SEP        28        33    |       37       115    |        40        45             32
                                                                    |                       |
==================================================================================================================================
                      POWDER & TONGUE RIVER BASINS                      |              POWDER & TONGUE RIVER BASINS
             Reservoir Storage (1000 AF) - End of May                   |        Watershed Snowpack Analysis - June 1, 1999
==================================================================================================================================
                                      Usable |  *** Usable Storage ***  |                            Number     This Year as % of
Reservoir                            Capacity|  This      Last          |   Watershed                  of       =================
                                             |  Year      Year     Avg  |                          Data Sites   Last Yr   Average
========================================================================|=========================================================
TONGUE RIVER                            68.0     65.0     26.8     48.2 |   UPPER TONGUE RIVER          5       855       142
                                                                        |
                                                                        |   GOOSE CREEK                 1         0       118
                                                                        |
                                                                        |   CLEAR CREEK                 2       2171      167
                                                                        |
                                                                        |   CRAZY WOMAN CREEK           1         0       269
                                                                        |
                                                                        |   UPPER POWDER RIVER          3         0       192
                                                                        |
                                                                        |   POWDER RIVER in WY          5       3214      174
                                                                        |
==================================================================================================================================
 * 90%, 70%, 30%, and 10% chances of exceeding are the probabilities that the actual volume will exceed the volumes in the table.

The average is computed for the 1961-1990 base period.

(1) - The values listed under the 10% and 90% Chance of Exceeding are actually 5% and 95% exceedance levels.                  
(2) - The value is natural volume - actual volume may be affected by upstream water management.
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